Treatment of saline, acidic, metal-contaminated groundwater from the Western Australian Wheatbelt.

Managing acidic, metal-containing saline ground and drainage waters in the Wheatbelt of Western Australia is an environmental and economic challenge. Sulfate-reducing fluidised bed bioreactors are shown to be technically capable of treating high salt, low pH, metal containing waters from the town of Narembeen in the Wheatbelt so as to reduce acidity and to remove most of the undesirable metal contaminants. The hydraulic residence time (HRT) limit for a stable process with groundwater from the region of Narembeen was >16 hours. The maximal rate of sulfate reduction in the laboratory system treating Narembeen groundwater was similar to rates observed in comparable applications of the process at other sites, ca. 3 g sulfate (L-reactor)(-1) day(-1). Salts that are relatively free of metal contaminants can be produced from water that has been treated by the sulfate-reducing fluidised bed bioreactor. It is unlikely that metal precipitates, captured from Wheatbelt waters by the process, would be of economic value. If sulfate-reducing fluidised bed reactors were considered technologically appropriate at larger scale, the decision to use them would be based on the necessity to take action, the comparative effectiveness of competing technologies, and the relative costs of competing technologies.

The isolation and use of iron-oxidizing, moderately thermophilic acidophiles from the Collie coal mine for the generation of ferric iron leaching solution.

Moderately thermophilic, iron-oxidizing acidophiles were enriched from coal collected from an open-cut mine in Collie, Western Australia. Iron-oxidizers were enriched in fluidized-bed reactors (FBR) at 60 degrees C and 70 degrees C; and iron-oxidation rates were determined. Ferrous iron oxidation by the microbiota in the original coal material was inhibited above 63;C. In addition to four iron-oxidizers, closely related to Sulfobacillus spp that had been earlier isolated from the 60 degrees C FBR, one heterotroph closely related to Alicyclobacillus spp was isolated. The Alicyclobacillus sp. isolated from the Collie coal mine tolerated a lower pH than known Alicyclobacillus spp and therefore may represent a new species. The optimum temperature for growth of the iron-oxidizing strains was approximately 50 degrees C and their maximum temperatures were approximately 60 degrees C. The FBR was adjusted to operate at 50 degrees C and was inoculated with all of the isolated iron-oxidizing strains. At 60 degrees C, an iron-oxidation rate of 0.5 g Fe(2+) l(-1) x h(-1) was obtained. At 50 degrees C, the iron-oxidation rate was only 0.3 g Fe(2+) l(-1) x h(-1). These rates compare favourably with the iron-oxidation rate of Acidianus brierleyi in shake-flasks, but are considerably lower than mesophilic iron-oxidation rates.

The role of microbial populations in the containment of aromatic hydrocarbons in the subsurface.

A survey of soil gases associated with gasoline stations on the Swan Coastal Plain of Western Australia has shown that 20% leak detectable amounts of petroleum. The fates of volatile hydrocarbons in the vadose zone at one contaminated site, and dissolved hydrocarbons in groundwater at another site were followed in a number of studies which are herein reviewed. Geochemical evidence from a plume of hydrocarbon-contaminated groundwater has shown that sulfate reduction rapidly developed as the terminal electron accepting process. Toluene degradation but not benzene degradation was linked to sulfate reduction. The sulfate-reducing bacteria isolated from the plume represented a new species, Desulfosporosinus meridiei. Strains of the species do not mineralise 14C-toluene in pure culture. The addition of large numbers of cells and sulfate to microcosms did stimulate toluene mineralisation but not benzene mineralisation. Attempts to follow populations of sulfate-reducing bacteria by phospholipid signatures, or Desulfosporosinus meridiei by FISH in the plume were unsuccessful, but fluorescently-labeled polyclonal antibodies were successfully used. In the vadose zone at a different site, volatile hydrocarbons were consumed in the top 0.5 m of the soil profile. The fastest measured rate of mineralisation of 14C-benzene in soils collected from the most active zone (6.5 mg kg(-1) day(-1)) could account for the majority of the flux of hydrocarbon vapourtowards the surface. The studies concluded that intrinsic remediation by subsurface microbial populations in groundwater on the Swan Coastal Plain can control transport of aromatic hydrocarbon contamination, except for the transport of benzene in groundwater. In the vadose zone, intrinsic remediation by the microbial populations in the soil profile can contain the transport of aromatic hydrocarbons, provided the physical transport of gases, in particular oxygen from the atmosphere, is not impeded by structures.

Using polymer mats to biodegrade atrazine in groundwater: laboratory column experiments.

Large-scale column experiments were undertaken to evaluate the potential of in situ polymer mats to deliver oxygen into groundwater to induce biodegradation of the pesticides atrazine, terbutryn and fenamiphos contaminating groundwater in Perth, Western Australia. The polymer mats, composed of woven silicone (dimethylsiloxane) tubes and purged with air, were installed in 2-m-long flow-through soil columns. The polymer mats proved efficient in delivering dissolved oxygen to anaerobic groundwater. Dissolved oxygen concentrations increased from <0.2 mg l(-1) to approximately 4 mg l(-1). Degradation rates of atrazine in oxygenated groundwater were relatively high with a zero-order rate of 240-380 microg l(-1) or a first-order half-life of 0.35 days. Amendment with an additional carbon source showed no significant improvement in biodegradation rates, suggesting that organic carbon was not limiting biodegradation. Atrazine degradation rates estimated in the column experiments were similar to rates determined in laboratory culture experiments, using pure cultures of atrazine-mineralising bacteria. No significant degradation of terbutryn or fenamiphos was observed under the experimental conditions within the time frames of the study. Results from these experiments indicate that remediation of atrazine in a contaminated aquifer may be achievable by delivery of oxygen using an in situ polymer mat system.

The formation of malodorous dimethyl oligosulphides in treated groundwater: the role of biofilms and potential precursors.

Water distributed from the Wanneroo Groundwater Treatment Plant intermittently contains dimethyl trisulphide (DMTS). The compound is responsible for a "swampy odour" in the water. DMTS production from potential precursors was insignificant in the absence of biofilms when compared with DMTS production from precursors in the presence of biofilms in a biofilm reactor. Greatest dimethyl disulphide (DMDS) and DMTS production (> 3000 ng L-1 DMTS) occurred in the reactors when supplied with methane thio-containing compounds, such as methionine, S-methyl cysteine and methyl-3-(methylmercapto)-propionate. Abiotic DMTS production from oligosulphides also occurred through the addition of the methylating agents, methyl iodide or methyl-p-toluene sulphonate. Significant DMTS production also occurred with Wanneroo water that contained added omega-thio-containing compounds such as cysteine (1400 ng L-1 DMTS), and 3-mercaptopropionate (210 ng L-1). Biomethylation, a ubiquitous response by microorganisms for the detoxification of toxic compounds, generated DMDS/TS from biofilm oligosulphides. Biofilms exposed to the toxic compounds selenate or 2,4,6-trichlorophenol methylated oligosulphides in addition to the toxins. Sodium sulphide also stimulated DMTS production. Easily Biodegradable Dissolved Organic Carbon (BDOC) probably contributed indirectly to DMTS production by the biofilms, although whether this was a result of its stimulation of greater microbial activity or consumption of oxygen, or both, remains unresolved. Stagnation of water in the biofilm reactors also increased DMTS production, which was concomitant with depletion of oxygen concentrations in the bulk water. Many processes, such as degradation of methane thio-containing compounds, methylation of sulphides and oligosulphides, and changes in contributions of different metabolic pathways upon depletion of oxygen concentrations upon water stagnation, probably contribute simultaneously to "swampy odour" production in the distribution system.

Desulfosporosinus meridiei sp. nov., a spore-forming sulfate-reducing bacterium isolated from gasolene-contaminated groundwater.

Eight strains of spore-forming, sulfate-reducing bacteria, isolated from groundwater contaminated with motor fuel [mostly benzene, toluene ethylbenzene and xylene (BTEX) compounds] in sandy soil near Perth, Australia, were closely related to Desulfosporosinus (previously Desulfotomaculum) orientis DSM 765T (95.3-97.3% 16S rDNA sequence similarity). Whole-cell fatty acids were dominated by even-carbon, straight-chain saturated and mono-unsaturated fatty acids, in particular 16:0, 16:1cis9, 14:0 and 18:1cis11. The strains grew at temperatures between 4 and 42 degrees C and in medium containing up to 4% NaCl. The eight strains clustered into two main groups based on phylogeny, randomly amplified polymorphic DNA (RAPD)-PCR patterns and nutritional characteristics. Representatives of the two groups, strain S5 (group A) and strain S10T (group B) had 81% DNA-DNA homology with each other and therefore should be accommodated in the same species. Strain S10T had less than 38% homology with Desulfosporosinus orientis DSM 765T, the most closely phylogenetically related type strain available. The new strains were distinguished from Desulfosporosinus orientis DSM 765T by different banding patterns in a RAPD-PCR, and phenotypically by their inability to utilize fumarate as a carbon and energy source with sulfate as the electron acceptor and by their lower tolerance to NaCl. The DNA G+C contents were 46.8 and 46.9 mol% for strains S5 and S10T, respectively (Desulfosporosinus orientis DSM 765T 45.9 mol%). It is proposed that these new strains be placed in a new species of the genus Desulfosporosinus. The name Desulfosporosinus meridiei is proposed, with strain S10T as the type strain (= DSM 13257T = NCIMB 13706T).

Spore-forming, Desulfosporosinus-like sulphate-reducing bacteria from a shallow aquifer contaminated with gasoline.

Previous studies on the geochemistry of a shallow unconfined aquifer contaminated with hydrocarbons suggested that the degradation of some hydrocarbons was linked to bacterial sulphate reduction. There was attenuation of naphthalene, 1,3,5-trimethylbenzene (TMB), toluene, p-xylene and ethylbenzene in the groundwater with concomitant loss of sulphate. Here, the recovery of eight strains of sulphate-reducing bacteria (SRB) from the contaminated site is reported. All were straight or curved rod-shaped cells which formed endospores. Amplification and sequencing of the 16S rDNA indicated that the strains were all sulphate reducers of the Gram-positive line of descent, and were most closely related to Desulfosporosinus (previously Desulfotomaculum) orientis DSM 8344 (97-98.9% sequence similarity). The strains clustered in three phylogenetic groups based on 16S rRNA sequences. Whole cell fatty acid compositions were similar to those of D. orientis DSM 8344, and were consistent with previous studies of fatty acids in soil and groundwater from the site. Microcosms containing groundwater from this aquifer indicated a role for sulphate reduction in the degradation of [ring-UL-14C]toluene, but not for the degradation of [UL-14C]benzene which could also be degraded by the microcosms. Adding one of the strains that was isolated from the groundwater (strain T2) to sulphate-enriched microcosms increased the rate of toluene degradation four- to 10-fold but had no effect on the rate of benzene degradation. The addition of molybdate, an inhibitor of sulphate reduction, to the groundwater samples decreased the rate of toluene mineralization. There was no evidence to support the mineralization of [UL-14C]benzene, [ring-UL-14C]toluene or unlabelled m-xylene, p-xylene, ethylbenzene, TMB or naphthalene by any of the strains in pure culture. Growth of all the strains was completely inhibited by 100 micromol l-1 TMB.

Isolation of Terrabacter sp. strain DDE-1, which metabolizes 1, 1-dichloro-2,2-bis(4-chlorophenyl)ethylene when induced with biphenyl.

Terrabacter sp. strain DDE-1, able to metabolize 1,1-dichloro-2, 2-bis(4-chlorophenyl)ethylene (DDE) in pure culture when induced with biphenyl, was enriched from a 1-1-1-trichloro-2, 2-bis(4-chlorophenyl)ethane residue-contaminated agricultural soil. Gas chromatography-mass spectrometry analysis of culture extracts revealed a number of DDE catabolites, including 2-(4'-chlorophenyl)-3,3-dichloropropenoic acid, 2-(4'-chlorophenyl)-2-hydroxy acetic acid, 2-(4'-chlorophenyl) acetic acid, and 4-chlorobenzoic acid.

Flavobacterium hibernum sp. nov., a lactose-utilizing bacterium from a freshwater Antarctic lake.

Four freshwater Antarctic lakes were examined for the presence of beta-galactosidase-producing bacteria using mineral medium enrichments and lactose. Enrichments from only one of the lakes produced growth and two strains were isolated that were very similar in phenotype and fatty acid profile, and shared considerable homology in their DNA (DNA-DNA hybridization = 93 +/- 7%). The strains were psychrotrophic with theoretical Tmax, Tmin and Topt of 30-31, -7 degrees and 26 degrees C, respectively. The beta-galactosidase in cell extracts had an optimal activity at 39 degrees C. The strains were Gram-negative rods, showed gliding motility, contained branched and hydroxy fatty acids, and menaquinone 6 as the major respiratory quinone. The strains did not form microcysts and utilized lactose while using ammonium ions as a source of nitrogen, and a range of other sugars. The G + C content of the DNA was 34 mol%. Phylogenetic analysis of one of the strains, by comparison of 16S rDNA sequences, showed that it was most similar, but not identical to, Flavobacterium columnare and '[Sporocytophaga] cauliformis'. Both species could be differentiated phenotypically from the Antarctic isolates. DNA-DNA hybridization of the Antarctic isolate with six different members of the Flavobacterium 16S rDNA cluster showed no strain with greater than 18% relatedness. The nearest type species to the Antarctic isolate in the phylogenetic analysis was Flavobacterium aquatile. The name Flavobacterium hibernum is proposed for the Antarctic strains, and the type strain is ATCC 51468T (= ACAM 376T).

Degradation of 2-nitrodiphenylamine, a component of Otto Fuel II, by Clostridium spp.

Otto Fuel II, a propellant in torpedoes, is composed of 76% 1,2 propanediol dinitrate (PGDN), 22.5% di-n-butyl sebacate, and 1.5% 2-nitrodiphenylamine (NDPA), and is largely recalcitrant to aerobic microbial degradation. Anaerobic microbial degradation of Otto Fuel II was tested by inoculating anaerobic enrichment media, containing either 2% (vol:vol) complete Otto Fuel II or 2% of a 0.02% solution of Otto Fuel II in methanol, with soil and water from sites contaminated with munitions or with landfill leachate. Anaerobic bacterial growth was completely inhibited by 2% Otto Fuel II. Two mixed bacterial enrichments developed in anaerobic media containing 2% (v/v) of a 0.02% solution of Otto Fuel II in methanol. After incubation, PGDN could not be detected in either enrichment, but was also not detectable in sterile controls, suggesting abiotic degradation of low concentrations of PGDN in reduced anaerobic medium. NDPA did not degrade in either enrichment. Similarly, complete Otto Fuel was recalcitrant to degradation by highly reducing methanogenic biomass collected from an upflow anaerobic sludge blanket bioreactor (UASB). A comparison of the degradative ability of autoclaved and viable biomass showed that low concentrations of PGDN autodegraded, however unlike the autoclaved anaerobic biomass, the viable anaerobic biomass degraded the NDPA component of Otto Fuel II. Two strains of anaerobic clostridia, strains SP3 and SPF, that caused the disappearance of NDPA at its limit of solubility in culture media, were isolated from the UASB bioreactor biomass. SP3 and SPF were shown, by comparison of 16S rDNA sequences, to be most closely related to Clostridium butyricum and Clostridium cochlearium respectively. Although NDPA was lost from cultures of both strains, metabolic end products were not identified. Neither strain could degrade NDPA unless supplied with an alternative energy source. In the culture system used, NDPA stimulated the growth of SP3 but it had no appreciable effect on the growth of SPF. Both SP3 and SPF degraded low concentrations of trinitrotoluene (TNT), without the production of detectable concentrations of aromatic amines. A possible method for the remediation of small spills of Otto Fuel II is suggested.

Methanogenium frigidum sp. nov., a psychrophilic, H2-using methanogen from Ace Lake, Antarctica.

Methanogenium frigidum sp. nov. was isolated from the perennially cold, anoxic hypolimnion of Ace Lake in the Vesfold Hills of Antarctica. The cells were psychrophilic, exhibiting most rapid growth at 15 degrees C and no growth at temperatures above 18 to 20 degrees C. The cells were irregular, nonmotile coccoids (diameter, 1.2 to 2.5 microns) that occurred singly and grew by CO2 reduction by using H2 as a reductant. Formate could replace H2, but growth was slower. Acetate, methanol, and trimethylamine were not catabolized. Cells grew with acetate as the only organic compounds in the culture medium, but growth was much faster in medium also supplemented with peptones and yeast extract. The cells were slightly halophilic; good growth occurred in medium supplemented with 350 to 600 mM Na+, but no growth occurred with 100 or 850 mM Na+. The pH range for growth was 6.5 to 7.9; no growth occurred at pH 6.0 or 8.5. Growth was slow (maximum specific growth rate, 0.24 day-1; doubling time, 2.9 days). This is the first report of a psychrophilic methanogen growing by CO2 reduction.

Microbial biomass in a shallow, urban aquifer contaminated with aromatic hydrocarbons: analysis by phospholipid fatty acid content and composition.

The city of Perth contains a number of sites that have been contaminated with hydrocarbons due to leakage from petroleum underground storage tanks. Microbial biomass in groundwater and sediment cores from above and below the water table, and from within and outside a plume of hydrocarbon contamination, was examined using phospholipid fatty acid methyl ester analysis. Microbial numbers, calculated from the phospholipid content, ranged from 0.9 x 10(6) to 7.8 x 10(6) 'Escherichia coli equivalent cells' g-1 dry wt of sediment. Over 96% of the microbial biomass was attached to the sediment and the proportion of attached cells did not decrease within the plume of contaminants. The amount of biomass within aquifer samples seemed to be related more to the proximity of the rhizosphere to the shallow aquifer, and other unknown urban inputs, rather than to the effects of the plume of contaminants. Fatty acids common to many bacterial groups dominated within the plume, and as such the analyses gave limited insight into microbial community structure. For site assessment of intrinsic remediation of shallow aquifers in urban areas, estimates of microbial biomass may not provide information that is readily applicable to plume management.

Reevaluating the classification of Paracoccus halodenitrificans with sequence comparisons of 16S ribosomal DNA.

The results of phylogenetic analysis in which 16S ribosomal DNA sequences were compared confirmed previous chemotaxonomic data which suggested that Paracoccus halodenitrificans is inappropriately placed in the genus Paracoccus, which belongs in the alpha subclass of the Proteobacteria. P. halodenitrificans should be placed in the family Halomonadaceae, which belongs in the gamma subclass of the Proteobacteria.

Phylogenetic relationships between some members of the genera Deleya, Halomonas, and Halovibrio.

The genera Halomonas and Deleya, which constitute the family Halomonadaceae, are difficult to differentiate on the basis of phenotypic and chemotaxonomic attributes. DNA-rRNA hybridization studies have indicated that some Halomonas spp. have the same level of relationship to the type species of the genus Deleya as some Deleya spp. A phylogenetic analysis of the 16S rRNA sequences of seven members of the Halomonadaceae indicated that the members of the genera Halomonas and Deleya do not form separate monophyletic subgroups, confirming the lack of any phylogenetic support for retention of these taxa as separate genera. A phylogenetic analysis of the 16S rRNA sequence of Halovibrio variabilis confirmed that this species belongs in the Halomonadaceae. All of the members of the Halomonadaceae examined and Halovibrio variabilis possess a cytosine residue at position 486 (Escherichia coli numbering), which is an extremely rare attribute among the prokaryotes and has been reported in only one other species, Listonella anguillarum. Several other signature characteristics which define this group in the gamma subclass of the Proteobacteria are identified. The Jukes-Cantor distances between members of the family Halomonadaceae, including Halovibrio variabilis, range from 0.086 to 0.000 (the levels of similarity between the 16S rRNA sequences range from 92.6 to 100%). The members of the genera Halomonas, Deleya, and Halovibrio form a monophyletic group and share common chemotaxonomic and phenotypic characteristics. Subgroups containing members of the genera Halomonas, Deleya, and Halovibrio cannot be resolved on the basis of phylogenetic, chemotaxonomic, or phenotypic data. Our data indicate that the members of the genera Halomonas, Deleya, and Halovibrio should be united in a single genus.

Direct sequencing of the polymerase chain reaction-amplified 16S rRNA gene of Flavobacterium gondwanense sp. nov. and Flavobacterium salegens sp. nov., two new species from a hypersaline Antarctic lake.

Phenotypic data and phospholipid ester-linked fatty acid profiles indicate that pigmented bacterial strains isolated from a hypersaline Antarctic lake are members of the "flavobacterium-bacteroides" phylum and may represent new taxa. Nearly complete 16S rRNA sequences were obtained for representative strains by directly sequencing the polymerase chain reaction-amplified 16S rRNA gene. Sequence signatures confirmed that these organisms were members of the flavobacterium-bacteroides phylum. A phylogenetic analysis, in which the sequences of the Antarctic strains were compared with a large number of sequences available for members of the flavobacterium-bacteroides phylum, showed that the Antarctic strains were phylogenetically distinct. The new species cluster with a group of organisms that contains the type species of the genus Flavobacterium, Flavobacterium aquatile. Two new species are described, for which the names Flavobacterium gondwanense and Flavobacterium salegens are proposed; strains ACAM 44 (= DSM 5423) and ACAM 48 (= DSM 5424) are the type strains of F. gondwanense and F. salegens, respectively.

Cell wall-less, free-living spirochetes in Antarctica.

The phylogeny of an Antarctic, cell wall-less, bacterial strain was determined by sequencing PCR amplified 16S rDNA, and comparison of the sequence with other bacterial 16S rRNA sequences available in databanks. Although the strain was phenotypically very similar to members of the genus Anaeroplasma, phylogenetic analyses showed it was a member of the order Spirochaetales. Until now, the order was one of the few bacterial orders in which phylogeny was reflected in a uniform morphology of its members. The viability of wall-less cells in cultures of spirochetes and spirochetal infective material warrants reinvestigation.

Psychrotrophic, lactic acid-producing bacteria from anoxic waters in Ace Lake, Antarctica; Carnobacterium funditum sp. nov. and Carnobacterium alterfunditum sp. nov.

Heterofermentative, lactic acid-producing, gram-positive, motile bacteria were isolated from the waters of Ace Lake, Antarctica. All strains produced virtually only L(+)lactic acid from D(+)glucose. D(--)-ribose was fermented to lactic, acetic, and formic acids, and ethanol. Cell walls contained meso-diaminopimaleic acid. The strains did not grow at 30 degrees C and were psychrotrophic. Whole cells contained 18:1 cis 9 as a major component of their fatty acids. At 20 degrees C, the strains grew better anaerobically than aerobically and all strains lacked catalase, oxidase and respiratory lipoquinones. DNA that coded for most of the 16S rRNA gene of one of the strains was amplified by the polymerase chain reaction and sequenced. The strain was phylogenetically most closely related to Carnobacterium mobile (Knuc = 0.0214). The isolates separated into two phenotypes. DNA/DNA homology studies determined on a representative from each phenotype showed low homology between the phenotypes (38 +/- 8%), and with Carnobacterium mobile (26 +/- 2%, 34 +/- 2%). Carnobacterium funditum sp. nov. produced acid from mannitol, trehalose, but not amygdalin. The G + C content of the DNA was 32-34%, and the Type strain is DSM 5970 (=ACAM 312). Carnobacterium alterfunditum sp. nov. produced acid weakly from amygdalin but not from mannitol trehalose. The G + C content was 33-34%, and the Type strain is DSM 5972 (=ACAM 313).

Microbial community structure and biomass estimates of a methanogenic Antarctic Lake ecosystem as determined by phospholipid analyses.

Phospholipid analyses were performed on water column particulate and sediment samples from Ace Lake, a meromictic lake in the Vestfold Hills, Antarctica, to estimate the viable microbial biomass and community structure in the lake. In the water column, methanogenic bacterial phospholipids were present below 17 m in depth at concentrations which converted to a biomass of between 1 and 7×10(8) cells/liter. Methanogenic biomass in the sediment ranged from 17.7×10(9) cells/g dry weight of sediment at the surface to 0.1×10(9) cells/g dry weight at 2 m in depth. This relatively high methanogenic biomass implies that current microbial degradation of organic carbon in Ace Lake sediments may occur at extremely slow rates. Total microbial biomass increased from 4.4×10(8) cells/ liter at 2 m in depth to 19.4×10(8) cells/liter at 23 m, near the bottom of the water column. Total nonarchaebacterial biomass decreased from 4.2 ×10(9) cells/g dry weight in the surface sediment (1/4 the biomass of methanogens) to 0.06×10(8) cells/g dry weight at 2 m in depth in the sediment. Phospholipid fatty acid profiles showed that microeukaryotes were the major microbial group present in the oxylimnion of the lake, while bacteria dominated the lower, anoxic zone. Sulfate-reducing bacteria (SRB) comprised 25% of the microbial population at 23 m in depth in the water column particulates and were present in the surface sediment but to a lesser extent. Biomass estimates and community structure of the Ace Lake eco-system are discussed in relation to previously measured metabolic rates for this and other antarctic and temperate ecosystems. This is the first instance, to our knowledge, in which the viable biomass of methanogenic and SRB have been estimated for an antarctic microbial community.

Gemmata obscuriglobus, a new genus and species of the budding bacteria.

A single strain of a budding bacterium was isolated from freshwater. The strain had a life-cycle, with a multitrichous swarmer stage, and produced a phase-dark inclusion of packed ribosomes and nuclear material. The mol % G + C of the DNA was 64.4 +/- 1.0. A new genus, Gemmata with the type species Gemmata obscuriglobus is proposed. The type strain is UQM 2246.